Glossary

 

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

 

 

 

A

 

Access Code
Similar to a password, this series of numbers or letters enables a user to access a system or computer.  At job sites an access code can be the system or process that oversees employees or cars both in and out of certain areas.

 

ActiveX
ActiveX is Microsoft software component technology, mainly used by Microsoft Windows.  They facilitate sharing of information between differing applications.  Digital video recorders utilize ActiveX to remotely view security cameras online.

 

AGC (Automatic Gain Control)

AGC increases the signal strength of security cameras when the light level decreases, and puts a cap on it during higher levels; this keeps the output signal consistent. 

 

AI (Auto Iris)
A useful feature to have in a video camera, an auto iris compensates for variations in light levels, from sunlight to shadows.  Essentially, the auto iris opens and closes the lens iris as the light changes; this also prevents the camera from being damaged by very bright sunlight.

 

ALC (Automatic Level Control)
Some security cameras feature ALC, which means the camera can bring out detail in bright or dark areas of an image.  If too much sunlight makes an image too dark, ALC can focus on the needed image.
 

Ambient Light Level
This is the amount of background light present at any specific time.

 

Analog Signal
Analog signals are produced by most security cameras.  Analog signals are continuously variable, and are greatly affected by ‘noise’ (disturbances) within the system, and recordings of analog information (such as videotapes) degrade over time.  This doesn’t occur with digital signals recorded on media like CDs, DVDs and computer hard drives.
 

Aperture
An aperture is a lens opening that controls how much light reaches the film or digital sensor.  Iris adjustment controls aperture size, and a series of f-stop numbers dictate how much light passes through the lens.  A smaller aperture allows for better focus on objects outside the camera’s plane of focus.

 

Aspect Ratio
Aspect Ratio refers to the ratio between an image’s height and width. Differing mediums such as television, HDTV, and film, use different aspect ratios.  Within computer graphics, it refers to the shape of an individual pixel in a digital image. 

 

Automatic White Balance ( top )
Cameras with this feature installed will automatically adjust color settings to achieve consistent quality in the white areas of the image.

 

B

 

Back Focus [top]
Cameras are focused by moving the image sensor in relationship with the lens, which enables differing back focal lengths for the lens.  This adjustment is called Back Focus and is important when fitting a zoom. 
 

BLC (Back Light Compensation) [top]
Cameras with this feature will automatically bring more detail to darker areas of an image when bright lights (usually shining from behind) obscure it.
 

bps (Bits Per Second) [top]
This unit is used to measure the speed data is moved between sources.  For example, a 56kbps modem can move 56,000 bits per second.

 

 Bullet Camera [top]
Named in reference to its shape, a bullet camera is a type of security camera similar to a spot cam.  Its limitation is a fixed focal lens (not zoom), but its small, narrow size makes it suitable for areas other cameras might not fit.

 

C

 

CCD (Charge Coupled Device) [top]
This is a computer chip that converts the light energy that enters a camera into an electrical charge, which is then converted into an electronic image.  The image is then optimized into a very high quality picture. There are two types of CCD: frame transfer and interline transfer. 

 

CCTV (Closed Circuit Television) [top]
CCTV refers to the use of television cameras for surveillance purposes.  Unlike broadcast television, all devices are linked directly, usually by cables.  CCTV pictures are viewed and/or recorded, but are not broadcast.  Usually involving analog cameras and recorders, CCTV is the precursor to digital network systems.
 

C-Mount [top]
This is a specific type of camera, as well as its corresponding lens mount.  The C-mount lens is found in older versions of security cameras, and has a flange back distance of 17.5mm.  In order to achieve a focused image, a 5mm ring must be inserted between the camera and lens. 
 

Coaxial Cable [top]
A cable with a central conductor that’s surrounded by a shield sharing its same axis is called a coaxial cable.  It’s used primarily for carrying high frequency or broadband signals.  RG59 video coaxial cable is used for digital video recorder (DVR) installations.

 

CODEC [top]
CODEC means compressor/decompressor and is any technology used to compress and decompress data.  It converts analogue input into digital, and then converts it back to analogue.  CODECS can be either software applications or hardware components, or both.  DVRs use CODECS to compress video streams from security cameras, and then store this compressed data on a hard disk. 
 

Composite Video [top]
This type of video is a combination of different source video signals, usually YUV, field, line, blanking pedestal, color sync, and field equalizing pulses.  The end result is one composite signal, allowing it to be modulated onto a RF carrier.
 

CS Mount [top]
CS mount lenses offer a longer focal distance than their C mount predecessors.  They have a flange back distance of 12.5mm.  Because they are more practical for compact cameras, CS mounts are used in most modern cameras.  A 5mm spacer ring (known as a C ring) enables CS cameras to also use a C mount lens.

 

D

 

Depth of field ( top )
This is the difference between the nearest and furthest points in a scene that remain in sharp focus.  Depth of field is dependent on the F-stop and focal length of the lens.

 

Digital Signal ( top )
A sequence of binary bits that represent ones and zeros makes up a digital signal.

 

Dome Camera ( top )
A common indoor security camera, dome cameras are mounted on the ceiling.  Their two main advantages are a more appealing visual appearance and being easily movable.  Their drawback is a lack of usefulness during low light situations (therefore not effective when the lights are off).

 

DSL (Digital Subscriber Line) ( top )
DSL is a digital telecommunications protocol that allows existing copper phone lines to be used for high-speed transfer of data between home and business end-users.  xDSL refers to the various types of Digital Subscriber Lines which include:  ADSL (Asymmetric DSL), SDSL (Single-line DSL), HDSL (High-data-rate DSL) and VDSL (Very-high-data-rate DSL).  In theory, ADSL (the most common of these types), allows for download speeds of up to 9 Mbps and upload speeds of up to 640 Kbps.  In reality, commercial performance is normally up to 1.544 Mbps download and 128 Kbps upload.
 

DVR (Digital Video Recorder)( top )
This device transforms analog video signals from security cameras into digital format, suitable for storage on a hard drive.  It also helps the user manage the stored video files, as well as providing motion detection settings and PTZ security camera control.  DVRs can often be remotely accessed over the Internet.
 

Dynamic IP address ( top )
This is the rotation of IP addresses such that every time a user logs onto the Internet, their IP address changes.  This is done for Internet security purposes, either by the user or by their ISP.  This process can interfere with the use of networked devices such as Network IP Cameras because they normally require a static IP address to function properly.

 

E

 

EI (Electronic Iris) ( top )
Certain CCD security cameras utilize an electronic iris to electronically mimic a traditional auto iris.  One drawback of an EI is that excessive light damages it over the long term. 
 

Electronic Shuttering ( top )
This term applies to video cameras that compensate for moderate indoor changes in light without use of auto iris lenses.
 

E-mail notification  ( top )
This is a feature of certain motion detecting Network IP Cameras.  When activity is detected, they can email authorized users images or video.  Griffid is one example of camera management software that accomplishes this.

 

Embedded operating system ( top )
Cameras with this can also operate as computers.  With an OS like Linux installed, they can perform other tasks such as sending images to a web site via FTP, email notification, and being simultaneously accessible by multiple users.
 

EMI (Electro Magnetic Interference) ( top )
If improperly shielded, most electronic equipment causes EMI.  The FCC sets the standards for electronic equipment shielding.
 

Ethernet ( top )
Ethernet can send information either wirelessly (known as WiFi) or, more commonly, over wires.  It runs at 10mbps, and all terminals connect to a single common bus (sometimes called a highway).  It serves as the IEEE (Institute of Electrical and Electronics Engineers) 802.3 standard, which ensures that networks adhere to a particular set of technical standards.   A new type, known as Fast Ethernet, or 100Base-T, runs at 100Mbps, and the newest type, Gigabit Ethernet, runs at 1gigabit per second. 

 

Event recorder ( top )
This type of recorder is kept in pause mode, and only records if activated by an alarm.

 

F

 

Fast lens ( top )
Having a larger iris (and smaller F-stop), a fast lens gathers and transmits increased light to a surveillance camera.

 

FI (Fixed Iris) ( top )
These widely used fixed focal length iris lenses are inexpensive and are found in smaller types of fixed CCTV security cameras, usually small case or dome cameras. 

 

Field of view ( top )
This is the total height and width of the view seen through the lens.
 

Firewall ( top )
A firewall is a software or hardware application installed on a home or office computer that is intended to prevent unauthorized users from accessing that computer.  With hacking and network intrusions on the rise, they are becoming essential in protecting private information.  Four popular types of firewall are packet filtering, application gateways, circuit-level gateways, and proxy servers.  Although they can be difficult to configure correctly, they are a critical component to protect unauthorized access and hacking of IP based surveillance systems that are LAN based.

 

f-number ( top )
This is used to indicate image brightness as formed by the lens and controlled by the iris.  The smaller the f-number, the brighter the image is.
 

Focal Length ( top )
Focal length is measured in mm or inches, and is the distance between the optical center of the lens and the point on which it focuses.  A lower focal length results in less magnification with a greater field of view, and vice versa for longer focal lengths.  Security cameras usually have a focal length of ¼”, 1/3”, or ½”.
 

fps (Frames Per Second) ( top )
In the field of video surveillance, fps means the number of frames a DVR is able to capture per second.  Three steps are required: video capture, compression, and storage.  Each step affects a DVR’s true fps number.  The use of DSP chips in both IP cameras and DVRs can assist in the optimization of fps.

 

Frame ( top )
One complete picture is called a frame, and it contains 525 lines (NTSC) or 625 lines (PAL). 

 

f-stop ( top )
The light gathering ability of a lens (known as a camera lens aperture setting) is indicated by an f-stop.  Using a smaller f-stop number results in a greater amount of light passing through the lens, as well as a shallower depth of field.
 

FTP (File Transfer Protocol) ( top )
FTP is a client/server protocol used for the exchange of data between computers.  Network cameras with an embedded operating system use FTP to send camera images to an authorized user’s computer or web site.

 

G & H

 

GUI (Graphical User Interface) ( top )
Pronounced ‘gooey’, this is the interface between the computer and the matrix switcher.  Active areas of the computer screen are programmable, feature menus, icons, are clickable, and able to activate devices such as VCRs and matrix switchers.  Essentially, the GUI makes the CCTV system easier to use.

 

Hertz ( top )
A Hertz (Hz) is the unit used to measure frequency, with 1 Hz equal to 1 cycle per second.

 

Horizontal hum bars ( top )
Sometimes called Venetian blinds because they are horizontal bars (either black or white) that extend across an entire picture.  They’re either moving or stationary, and are the result of roughly a 60 Hz interfering frequency (usually from a 60 Hz AC power source). 

 

Horizontal resolution ( top )
This measures the maximum amount of individual picture elements recognizable in a single scanning line. ( top )

 

HTML (HyperText Markup Language) ( top )
HTML is the language used in the creation of WWW pages, with use of hyperlinks and markup for text formatting. 

 

HTTP (HyperText Transfer Protocol) ( top )
This is the protocol utilized to transmit and request information from WWW servers to browsers, either online or over networks.

 

Hub ( top )
Networks rely on devices called hubs to connect multiple computers together into a LAN.  Standard hubs share the bandwidth across all ports (so an eight port 100 Mps hub allocates this 100 Mps among the eight ports), while switching hubs are able to give each individual port a dedicated bandwidth amount (so these same eight ports could conceivably each receive a full 100 Mps of bandwidth on a switching hub).

 

 I-J

 

Infrared camera ( top )
These cameras are well suited for surveillance of low light areas or areas with no light at all.  Infrared LEDs surround the lens and shine infrared light, illuminating the scene.  They usually have a fixed focal length lens, and present b/w images during low light (though some offer color in the day and b/w at night). 

 

Infrared detector ( top )
This is an alarm that uses infrared light to detect nearby movement.

 

Infrared illuminator ( top )
A light source working in the infrared frequency range is called an infrared illuminator.

 

Interlaced ( top )
This refers to a type of display where the electron beams alternate between scanning the even numbered lines and then the odd numbered lines, resulting in the two vertical scans on the screen, with the field (each set of lines) being updates 60 times a second, and with the frame (both fields) updated 30 times a second.

 

 

Interleaving ( top )
Some alarms and security systems use the process of interleaving to add extra frames from alarmed cameras to a time multiplexed sequence while the alarm is activated.  This prioritizes the view from alarmed cameras in the sequence of camera views.

 

IP (Internet Protocol) ( top )
This is the protocol used to route a packet of data from source to destination over the Internet.  Every computer on the Internet has a different IP address that identifies it from other computers.

 

IP address ( top )
This is a numeric address that is then translated into a domain name by the DNS (domain name server).  When we type in a website’s name, the computer translates this into its IP address, which is a unique 32-bit number.  The TCP/IP protocol then uses it for routing the data packets to their destinations.  Each host has a unique IP address.

 

IP Camera (or Network Camera) ( top )
This signal from an IP camera is delivered over an IP network.  The camera digitizes the images, compresses them, and then sends them over the network (if this sounds similar to a webcam, that’s because there is digital webcam technology contained within a network camera).  But a typical IP network camera is much more advanced as compared to a consumer web camera which needs to be attached to a computer to operate.  IP enabled security cameras usually offer a browser interface so that the user can operate and view the video remotely over the Internet.  A DVR system is often comprised of an IP camera and a NVR.

 

Iris ( top )
The section of the lens adjusted to control how much light passes through it and onto the CCD chip is called an iris. 

 

 

JPEG (Joint Photographic Experts Group) ( top )
This is one of the most common file formats for compressed photo images. A small amount of data, though not noticeable enough to be significant, is lost in the compression process, making JPEGs a lossy compression.

 

 K-L

 

LAN (Local Area Network) ( top )
A LAN is a high-speed network connecting computers that are nearby (probably in the same building), and offers differing connection protocol options.

 

Lens ( top )
This is the device responsible for focusing the image on the CCD, and most offer adjustable focal length and aperture.

 

Level control ( top )
Level control is control of the main iris, and sets the auto-iris circuit to a specific video level of the user’s choice.  The iris is therefore set to maintain this video level no matter what the light condition may be.  A high level opens the iris; a low level closes it.

 

Light sensor ( top )
Often used to turn infrared illuminators on or off, this device is triggered when it detects a pre-set amount of light, and helps cope with low (or no) level light conditions.

 

Linux ( top )
Linux is an open source UNIX implementation, and a popular alternative to the Windows operating system.  It is often used in embedded operating systems found in advanced Network IP Cameras.  Linux is freeware.

 

Loss Prevention ( top )
Best summarized as ‘not having anything stolen’, loss prevention is the practice of securing devices or information from theft or loss.  Video surveillance is a common practice in preventing theft or other losses of property like vandalism.

 

Lumen ( top )
A lumen (abbreviated as lm) is a unit that measures the visible power output of a light.  While watts measure the power the bulb needs, lumens measure the visible light that the bulb generates.

 

Lux ( top )
Used more often than lumens when discussing security cameras, a lux is a unit of illumination. It measures the amount of uniform light that falls on one square meter (expressed in one lumen per square meter).  Security camera specs use the lux to indicate how much light they require to operate, with lower lux levels indicating a camera as more effective in lower ambient light.  Look for 0.2 lux or less when choosing a low-light camera, and 2 lux or higher for daylight cameras.

 

M

 

MJPEG (Motion JPEG) [top]
Even though it’s not as efficient as MPEG-4, the MJPEG is still an effective way of creating video from the sequencing of JPEG images.  The video from store security cameras often uses this method when being formatted. 

 

 

MPEG-4 [top]
MPEG4 has a newer codec and supports 3D content, low bit rate encoding, and support for Digital Rights Management, which controls the use of copyrighted digital work.  MPEG4 is used for web streaming media, broadcast television, videophones, and CD distribution.  MPEG-4 is widely used in video surveillance, and has recently been improved to the AVC standard.

 

N - O

 

Network Camera [top]
Also known as a Network IP Camera, this is a stand-alone camera that uses a standard web-browser to view live, full motion video from a computer network, including over the Internet.  They often feature an embedded OS (operating system) and features like:  FTP of images, web server capability, and built-in motion detection.

 

NTSC (National Television Standards Committee) [top]
The NTSC represents the American and Japanese standard television video signal format of 525 picture lines and a 60Hz field frequency.

 

 

NVR (Network Video Recorder) [top]
Functionally similar to a DVR, a NVR also accepts IP camera inputs.  NVRs can be software based, making them suitable only for accepting IP camera streams over the Inter

 

Ohms [top]
These are units that measure the impedance or resistance of an electrical device.

Outdoor Camera Housing [top]
A protective shell for security cameras to be placed in outdoor environmental conditions, these housings typically include cooling fans for summer use and heaters for winter use. The heaters also eliminate fogging of the glass anytime this occurs.

 

 

Outdoor Dome Housing [top]
This housing is dome shaped for insertion of dome security cameras, is very tamper resistant, and allows for PTZ.

 

P

 

PAL (Phase Alternating Line) [top]
Europe’s television video signal standard is known as PAL.  PAL uses 625 picture lines and a 50Hz field frequency, and is incompatible with NTSC.
 

Pelco-D [top]
This Pelco created protocol is used to control PTZ security camera movement.
 

Photon [top]
A photon is the basic unit of light.

 

Pinhole Camera [top]
Perfect for covert surveillance, this quarter sized camera is nearly impossible to detect.  With it’s small size comes limited abilities though, primarily a small lens and limited zoom capabilities.
 

Pixel (Picture Element) [top]
Pixels are the smallest possible display unit of visual information available for building a graphical image.  It is also the basic unit of a CCD chip, with most CCD chips being comprised of over 300,000 pixels.

 

PoE (Power over Ethernet) [top]
This abbreviation refers to a method of supplying power to an IP camera using Category 5 Ethernet cables over a physically wired LAN network.
 

Post-Record [top]
Sometimes referred to as post-record time, this is a DVR's ability to record after a motion detection event has occurred.  It records for a specified amount of time after the event has been triggered, even though the motion may have ceased.
 

Power supply [top]
Most security cameras utilize 24V AC or 12V DC power supplies.  A power supply is usually plugged into a regular electrical outlet or part of a centralized power supply.

 

PPP (Point-to-Point Protocol) [top]
Point-to-point Protocol is the primary method used in establishing a direct connection between two devices on a network (usually a computer and the Internet). It is a communication protocol between computers using one of several methods: usually TCP/IP, telephone lines, or ISDN.
 

Pre-Record [top]
This DVR capability will record video prior to motion being detected, then send to the disk as much prior video as memory allows and video of the motion itself. 
 

Protocol [top]
Protocols are standard procedures used for regulating data transmission between computers.  Protocols exist to minimize errors during the exchange of data. 
 

PTZ Camera [top]
PTZ stands for Pan, Tilt, and Zoom.  These cameras are usually remotely controlled by software or a joystick.  PTZ cameras are used when active real time monitoring with the ability to point the camera’s viewing area to a specific action or event is desired. 
 

PTZ controller [top]
The controller used to control PTZ camera movement, usually software or a joystick.

 

Q - R

 

Raster [top]
A raster is a rectangular scan pattern of lines that the picture is created upon.  It also refers to an active TV monitor that has no video information displayed. 
 

Real Media [top]
Real Networks developed an early multimedia protocol for video and audio (often streaming) called Real Media. 
 

Real time video [top]
Any picture having 24 or more frames per second appears continuous, or in real time. 
 

Remote monitoring [top]
This allows an off site user to monitor surveillance camera feeds, so a user can survey a site regardless of their location from it.  The transfer of data from camera to user can be either over the Internet or the Ethernet, with IP cameras being suited to the task.
 

RG-11 [top]
Having a thick center core, this type of coaxial cable is used to transmit video signals of up to 550m.
 

RG-59 [top]
More commonly used than RG-11 for CCTV, this coaxial cable transmits video signals of up to 230m.
 

RGB (Red Green Blue) [top]
These are the three primary colors of light.  All other colors are derived from their mixture.
 

Router [top]

 is a piece of equipment facilitating the exchange of packets throughout LAN or WAN networks.  It moves packets across a predetermined path to their destination by storing and forwarding the packets, and then determining their optimal path along the network.  A router is hardware based, but can also include software.
 

RS232 (or RS-232) [top]
This is the communication standard that applies to PC serial communications.  RS232 is commonly used as the mechanism for sending instructions that control PTZ security camera movement.
 

RTP (Real-time Transport Protocol) [top]
The Internet Engineering Task Force (IETF) developed RTPs to specify audio and video signal management.  It standardizes the packet formatting for both for easy synchronization and Internet delivery.  Streaming media systems and video conferencing systems use RTP, while DVR systems rely on this protocol in the implementation of the remote view feature.  Since it doesn’t specify how video surveillance playback is implemented, the data from different RTP based surveillance systems usually cannot interoperate.
 

RTSP (Real Time Streaming Protocol) [top]
This open standard for Internet streaming of audio and video is popular among DVR makers for remote viewing of live or stored security camera video over the Internet.  RTSP controls the transmission of the data stream much the way a television remote controls the television.  Like RTP, interoperability problems exist between different DVR systems.

 

S

 

Scanning [top]
Applied to the field of video surveillance, scanning is the panning of a camera across the horizontal field of view. 
 

Security Camera [top]
The traditional CCTV camera is a multipurpose device capable of numerous configurations and superb quality.  They usually don’t include a lens, mount, or enclosure.  They also can be expensive to configure in comparison to cameras designed for a specific purpose. 
 

Sensitivity of a surveillance camera [top]
This term refers to the minimum level of light the CCD chip needs to generate an acceptable video picture, and is measured in lux.
 

Shutter speed [top]
This is the speed which the CCD chip can read out the charge.  Using either dipswitches or a surveillance camera’s menu (if one has been built in), the default setting of 1/50 sec (PAL) or 1/60 sec (NTSC) can be increased up to 1/100,000.
 

SMTP (Simple Mail Transfer Protocol) [top]
This is the standard server-to-server protocol for the delivery of electronic mail, either via Internet or on other TCP/IP networks.
 

SNR (Signal-to-Noise Ratio) [top]
SNR measures the ratio between the usable video signal and noise or interference.

 

Spot Cam [top]
Spot Cams are effective security cameras, useful for general surveillance needs.  They are intended to be operable out of the box (mounting bracket often not included), and most have their own integrated varifocal lens.  Be certain to choose a Spot Cam with its own auto iris feature and day/night capability. 
 

Static IP address [top]
This is an IP address that doesn’t change.  Any computer can connect to it, thereby making video surveillance systems with static IP addresses remotely accessible from any location on the Internet.
 

S-Video [top]
Representing an improvement in quality over composite video, S-Video separates chrominance and luminance onto two different signal wires, resulting in better picture quality.
 

Synchronization [top]
Frame formation in multi surveillance camera systems is started simultaneously by the process of synchronization, and there are differing ways this process can be achieved.

 

T - U
 

TCP/IP (Transmission Control Protocol/Internet Protocol) [top]
These protocols enable communication between differing computer and computer networks.  The IP is a connectionless protocol that provides the packet routing, while the TCP is connection based to provide reliability in communication and multiplexing.